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><A
NAME="INTRO-WHATIS"
>What is <SPAN
CLASS="PRODUCTNAME"
>PostgreSQL</SPAN
>?</A
></H1
><P
>   <SPAN
CLASS="PRODUCTNAME"
>PostgreSQL</SPAN
> is an object-relational
   database management system (<ACRONYM
CLASS="ACRONYM"
>ORDBMS</ACRONYM
>) based on
   <A
HREF="http://db.cs.berkeley.edu/postgres.html"
TARGET="_top"
>   <SPAN
CLASS="PRODUCTNAME"
>POSTGRES, Version 4.2</SPAN
></A
>,
   developed at the University of California at Berkeley Computer Science
   Department.  POSTGRES pioneered many concepts that only became
   available in some commercial database systems much later.
  </P
><P
>   <SPAN
CLASS="PRODUCTNAME"
>PostgreSQL</SPAN
> is an open-source descendant
   of this original Berkeley code.  It supports a large part of the SQL
   standard and offers many modern features:

   <P
></P
></P><UL
COMPACT="COMPACT"
><LI
><SPAN
>complex queries</SPAN
></LI
><LI
><SPAN
>foreign keys</SPAN
></LI
><LI
><SPAN
>triggers</SPAN
></LI
><LI
><SPAN
>views</SPAN
></LI
><LI
><SPAN
>transactional integrity</SPAN
></LI
><LI
><SPAN
>multiversion concurrency control</SPAN
></LI
></UL
><P>

   Also, <SPAN
CLASS="PRODUCTNAME"
>PostgreSQL</SPAN
> can be extended by the
   user in many ways, for example by adding new

   <P
></P
></P><UL
COMPACT="COMPACT"
><LI
><SPAN
>data types</SPAN
></LI
><LI
><SPAN
>functions</SPAN
></LI
><LI
><SPAN
>operators</SPAN
></LI
><LI
><SPAN
>aggregate functions</SPAN
></LI
><LI
><SPAN
>index methods</SPAN
></LI
><LI
><SPAN
>procedural languages</SPAN
></LI
></UL
><P>
  </P
><P
>   And because of the liberal license,
   <SPAN
CLASS="PRODUCTNAME"
>PostgreSQL</SPAN
> can be used, modified, and
   distributed by anyone free of charge for any purpose, be it
   private, commercial, or academic.
  </P
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